An expansion valve is usually arranged in a circuit of a refrigeration cycle system. The expansion valve controls the opening of the valve by sensing the superheat degree at an outlet of an evaporator or a suction section of a compressor in the refrigeration system, so as to realize the flow regulation as well as throttling and pressure reduction of the refrigerant in the system.
Please refer to FIG. 1, in which the structural schematic view of a typical expansion valve is shown.
Usually, the expansion valve is provided with an inlet pipe 900 and an outlet pipe 400. High-pressure fluid from a condenser enters from the inlet pipe 900, and flows towards the evaporator from the outlet pipe 400 after having been throttled and reduced in pressure. The upper end of the expansion valve includes air tank head 100 and driving rod 200, the driving rod 200 is connected with a valve core 500. A valve seat 1000 is provided at the joining position of outlet pipe 400 and the inlet pipe 900. The valve core 500 fits with the valve seat 1000 and abuts a supporting component 700 via a spring 600.
The bottom portion of the supporting component 700 is connected with an adjusting rod 800. The valve core 500, the supporting component 700 and the spring 600 are disposed in valve housing. The adjusting rod 800 is fixed to an adjusting seat.
A temperature sensing bulb is arranged at the outlet of the evaporator, which senses the temperature at the outlet of the evaporator. When the temperature is too high, the pressure of the working medium in the temperature sensing bulb is increased and transferred through capillary tube to the diaphragm in the air tank head. In this way, the diaphragm is moved downwards, and the driving rod 200 is driven to push the valve core 500 away from the valve seat 1000, such that the valve core 500 is able to control the size of the connecting opening between the inlet pipe 900 and outlet pipe 400 by the pressure generated from the temperature sensing bulb.
Furthermore, high-pressure condensation pressure from the inlet pipe 900 applies a force in a direction of opening the valve to the valve core 500, and the evaporation pressure from the outlet pipe 400 applies a force in a direction of closing the valve to the valve core 500. Therefore, besides the pressure from the temperature sensing bulb which opens the valve core 500 as well as the evaporation pressure and the spring force which close the valve core 500, the valve core 500 will additionally bear the force resulted form the differential pressure between high pressure and low pressure. As for the valve with small capacity or low-pressure refrigeration system, the force which is applied to the valve core 500 and resulted from the differential pressure between high pressure and low pressure imposes little influence on the system, however, as for the valve with large capacity or high-pressure refrigeration system, the force which is applied to the valve core 500 and resulted from the differential pressure between high pressure and low pressure will impose significant influence on the system. In this case, the superheat degree of the expansion valve is unable to reflect the true superheat degree of the evaporator, and the working efficiency of the system is greatly reduced. Furthermore, if the expansion valve having such structure is applied to the system such as heat pump which requires bidirectional operation, the force which is applied to the valve core 500 and resulted from the differential pressure between high pressure and low pressure when the system is operated in the refrigerating mode is just opposite to that when the system is operated in a heating mode, which makes it impossible to keep the static superheat degree identical in the two directions, such that the working efficiency reduction in one cycle of refrigerating mode or heating mode will become more significant.
In order to solve the above problems, some improvements are made to the structure of the valve core 500 in the prior art, i.e. machining a through hole in the valve core 500, so as to balance the pressure from the inlet pipe 900 by interior and exterior end surfaces of the valve core 500. Nevertheless, such expansion valve has instable performance since it realizes the force balance by the valve core 500 applied with forces. In addition, the valve core 500 has complex structure, large weight, large material consumption, and at the same time the load applied to adjusting spring 600 will increase. Furthermore, it is complex and inconvenient to connect, manufacture and assemble the adjusting rod 800 and supporting component 700.
Therefore, the technical problem to be solved by those skilled in the art is to provide an expansion valve which is able to balance the influence of the differential pressure between high pressure and low pressure on the valve core more steadily.